Method of preparing organic thionitrites



Patented July 27, 1943 2,335,391 ma'rnon or rnarsnme enema mourrarrasRichard 8. George, State College, Pa., and George S. Grands-ll and EdwinM. Nygaard, Woodbury, N. 1., assignors to Socony-Vacuum Oil Company,Incorporated, New York, N. E, a corporation of New York No Drawing.Application June 4, 1940, Serial No. 338,736

I (CL 260-453) therein of an organic thionitrite. we are aware of thefact that organic thionitrites have heretoiore been proposed for use asimproving agents for Diesel fuels, and our invention is especiallyconcerned with an improved method for preparing the organic thionitriteand the Diesel fuel blend containing same. United States Patent No.2,169,186 discloses the idea of employing organic thionitrites as Dieselfuel improving agents. The thionitrites obtained according to thedisclosure of that patent are prepared by the reaction of a mercaptanwith nitrosyl chloride. This reaction is represented in the patent bythe following equation:

in which R is said to represent an alkyl or aryl group; X is sulfurand/or oxygen; and m is a whole number having a value not greater than2. When x is oxygen and m is 1, the second reactant is nitrosylchloride. We have discovered that when the thionitrite is preparedaccording to the procedure described in this patent, it is of relativelylow stability; and although ganic thionitrites which have high ignitionquality and wherein the thionitrite content is of a high degree ofstability. It possesses the imther advantage 01' providing means wherebythe thionitrite can be manufactured in commercial quantifies fromreadily available raw materials without excessive loss or materials andwithout complicated processing. Although the invention is primarilyconcerned with the production of improved Diesel fuels, the method forforming the thionitrite lends itself to the recovery or this product inthe pure state. Our invention, therefore, contemplates both the methodin which the thionitrite is finally obtained in a Diesel fuel oil blendand in which the pure product is recovered. The method contemplatedherein may be broadly described as comprising the interreactlon of athiol compound with an alkali nitrite and a mineral acid in anon-homogeneous liquid systom comprising an aqueous phase and anonaqueous phase, which latter phase is a solvent for the thionitritecorresponding to the thiol compound and possesses the further propertyof substantial immiscibility with water.

In the event the ultimate product is to be a Diesel fuel blend, thenon-aqueous phase or the liquid system above referred to shouldpossessthe further property of miscibility with the fuel it'does possess theproperty of decreasing the ignition delay period, as indicated by thecetane number of a Diesel fuel, such decrease is not of the high orderobtained by thionitrites prepared.

according to the procedure of the present invention. The instability ofthese thionitrites. which may account for their low degree ofeflectiveness. is possibly explained by the fact that nitrosyl chlorideand hydrochloric acid, both of which are present in the reaction mixtureand are diilicult of removal, act to accelerate the decomposition of thethionitrite.

The method of the present invention lends itsell to production of Dieselfuels containing or-" oil-that is, it should be capable of being blendedwith a fuel suitable for compression ignition engines without seriousloss oi ignition quality of the blended fuel as compared with theunblended fuel. This non-aqueous phase should, oi course, be a materialhaving a low degree oi reactivity toward the reagents used and should beinert toward the thionitrite formed as the reaction product. Examplesoi, solvents which may be successfully used in the process contemplatedherein are petroleum fractions such as Diesel iuel'oiland Stoddardsolvent, alcohols such as iusel oil having low solubility in water, andorganic ethers. Y

The. thiol compounds which may be used in the process 01' this inventionare those compounds characterized by the'presence of the thiol (SH)group or their metal derivatives characterized by the presence of the SMgroup. Examples of such compounds are the alkyl mercaptans. thiophenols,thiolic acids and thionothiolic acids and their metal derivatives, whichcompounds may be typified by the general formulae: RSH, RSM, RCXSH andRCXSM, in which R represents alkyl, alkaryl, aralkyl, and aryl; Xrepresents oxygen or sulfur; and M represents a metal, preferably analkali metal.

The reactions involved in the method contem- V plated herein with thevarious typical thiol compounds referred to are illustrated by thefollowing equations:

acid. For use as the mineral acid in this reaction 25 preference isgiven to H] and H2804. The nitrous acid released reacts with the SHgroup of the thiol compound to form the thionitrite. If the metalderivative of the thiol compound is employed, it is necessary to use asufilcient quantity of mineral acid to convert the SM group to the SHgroup for reaction with the nitrous acid.

The general procedure in carrying out the process involves forming thenon-homogeneous liquid system of the type hereinabove referred to, whichsystem contains the inorganic nitrite and the thiol compound. The systemis then vigorously agitated to bring the two phases into intimatecontact, and the mineral acid is slowly added thereto. The thionitriteas it is formed oes into the nonqu ous phase of the system; and afterthe reaction is complete, the nonaqueous solution containing thethionitrite may be separated and either added to a Diesel fuel oil orfurther treated to recover the pure thionitrite.

Since many of the thionitrites are relatively unstable. it is desirableto carry out the reaction at relatively low temperature, although forsome compounds such as the tertiary butyl thionitrite the reaction maybe carried out at room temperature. In general, however, it ispreferable to employ temperatures ranging from to +20 C., dependinguponthe stability oi. the product. The quantity of the alkali nitriteused should be slightly in excess of that required to convert themercaptan to the thionitrie; and, as indicated above, the quantity ofmineral acid used should be substantially equivalent to the alkalinitrite in case a mercaptan is used as the thiol reactant and should beequivalent to the mercaptide and the nitrite in case a mercaptide ormetal derivative of the thiol compound is used.

The general procedure described above'may be carried out by forming asolution of a mercaptan or other thiol compound in fusel oil, or othersuitable solvent meeting the aforesaid requirements, of -such aconcentration as will yield an approximately 20 per cent blend of thethionitrite, assuming a quantitative conversion. This non-aqueoussolution is then mixed with a water solution or sodium nitrite in aquantity slightly in excess or that required to convert the thiolcompound to the thionitrite.. The mixture is then preferably cooled to atemperature 75 at which the thionitrite product will have a relativelyhighdegree of stability. In general this temperature is within the rangeof 20 to +20 C. After the reaction mixture has been cooled.

concentrated hydrochloric acid, in molecular equivalent quantity to thethiol compound, with about 1% times its weight of ice is added, withstirring and continued cooling, at such a rate that the temperature ofthe reaction mixture thiol compound.

Instead of adding the thiol compound in solution in the non-aqueoussolvent. it may be added to the aqueous phase as an alkaline solution ofthe thiol compound, in which case, as aforesaid,

I a sufilcient quantity of acid must be added to liberate the thiolcompound as well as the nitrous acid necessary for the reaction. Thilatter modification of the procedure is of particular applicability tothe utilization of the mercaptans removed from petroleum products bycaustic washing.

After the reaction is complete, the two phases are permitted toseparate, separation of the phases being facilitated by the addition ofsolid sodium chloride. The non-aqueous phase containing the organicthionitrite is separated from the aqueous phase, and, after filtrationthrough a clarifying medium such as paper or glass wool, it isready forblending with the Diesel fuel oil. In preparing blends from solutions ofthe type obtained according to the foregoing general procedure, theproportions are calculated on the assumption of 100 per cent conversionof the thiol compound to the thionitrite. Inthe event it is desired toisolate the thionitrite, this is preferably accomplished by using etheras the organic solvent. The ether solution or thionitrite may beconcentrated and distilled at reduced pressure in oneoperation to obtainthe thionitrite as a final product.

Further details in the procedure contemplated herein are illustrated bythe following specific example, which describes the preparation oftertiary butyl thionltrite in solution in a Diesel fuel oil.

Example Two kilograms of a straight run No. 2 Diesel fuel were placed ina three-necked, three-liter flask fitted with a mechanical stirrer,thermometer, and dropping funnel. The flask was immersed in a dry-icecooling bath and chilled to approximately 5 C. to 0 C. To the chilledoil was added a solution of 26 grams (0.36 mole) of 96-98% sodiumnitrite dissolved in 100 cc. of water. Then 30 grams (0.33 mole) oftertiary butyl mercaptan was added to the well-stirred mixture. Whilethe temperature was maintained between 5 and +3 C., grams (0.38 mole) ofconcentrated hydrochloric acid mixed with grams of ice was slowly addedat such a rate that the temperature did not rise appreciably. Almostimmediately on the addition of the acid the typical red-green dlchroismof tertiary butyl thionitrite became evident. After addition of the acidthe mixture was stirred for one-half hour at ap proximately 0 C. Theoil-water mixture was then filtered through glass wool, the aqueouslayer drawn oil and the oil layer filtered through pap r.

To demonstrate the effectiveness of Diesel fuels containing organicthionitrites prepared according to the procedure contemplated herein wehave conducted a series of tests with Diesel fuel blends containingtypical organic thionitrites. In these tests the ignition quality of theDiesel fuel blends was determined by the ignition delay method in aconverted C. F. R. engine, the results thereof g expressed as cetane'numbers (C. N.). The octane number is the per cent by volume of cetanein a blend of c'etane and alpha methyl naphthalene, which blended fuelhas the same combustion characteristics as the sample being tested (seeProc. A. S. T. M.,'vol. 38. 1, page 892). The

fuel used in obtaining the results which aretabulated in Table 1 belowwas a straight run No.

2 Diesel fuel oil distillate from Oklahoma City crude having a cetanenumber of 52. The renitrites prepared according to the procedure ofsuits set rel-tn in Table I were obtained with thiothe invention. Theblank fuel in the samples indicated by (a) and (b) contained no otheragent the Diesel fuel blend prepared accordingto the procedure describedin the example above. The blank fuel in samples (c)' to (h) inclusivecontained as a stabilizer for the thionitrite a quantity of fusel oilequal to from 2 to 2% times the concentration of the thionitriteused inthe sample. Thefusel oil was employed solely for the p rp se ofstabilization, as disclosed in cothe smallquantityof sludge formed wasemplayed in preparing the blends set-forth in Table II below. It will beobserved that with equal amolmts or the thionitrites obtained accordingto theprocedure or the patentthe increase in cetane number was less thanhalf that obtained with thionitrites prepared according'to the procedureIn the foregoing tables the concentration of the thionitrite in theDiesel fuel was calculated from the. amount of thiol compound employedin the reaction on the assumption of 100 per cent conversion to thethionitrite. In this latter regard it is to be understood thatthequantity or thionitrite used may bevaried depending upon the type orfuel with which it is blended and the ignipending application Serial No.338,737, flied June 4,, 1940, and made no contribution to the cetanenumber of the'blend.

tion properties desired in the blend. .Thethionitrites preparedaccording to the method of the present invention may be used in amountsvaryin! mm 0.1 per cent to 10.0 percent, but for 1 most purposes and formost fuels; concentrations.

in. the neighborhood of 0.25 per cent to 5.0 percentwillgivethedesiredresults.

Table I Thiol compound from which :35; C. N. of C. N. of Increasethionitrite was prepared g wt blank blend in C. N.

(a) Tertiary butyl mercaptam. 2. 0 52. 0 I 05. 5+ 13. 5+

Do 1.0 52.0 55.5 13.5 0.5 52.0 55.5 13.5 Do 0.25 52.0 59.0 7.0 (0) Mixedamyl mercaptan l. 0 52 0 62. 0 10.0 0. 25 52. 0 59. 0 7. 0 1. 0 52. 055. 5 13. 5 0. 5 52. 0 61. 0 9. 0 (d) Bsnzyl mercaptani. 0 52 0 55. 0l3. 0 (e) Psntamethylene dlmer-' captan 1.0 52. 0 64. 0 12. 0 (p p-Tolylmercaptam. l. 0 52. 0 1 05. 5+ 13. 5+ 5) Thin ropionic acid 1.0 52.0 05.5 13. 5 Thio nzolc'acid 1.0 52.0 58.0 0.0

l3lends reported as having cetsne number of 655+ have an actual ignitionquality of better than 05.5 cetane number; the actual lfimngstnumbercould not be determined under the conditions of I The "mixed amylmercapmn used in re ring these samples was a mixture of various isomersobtained t a open market.

The "crude ethyl mercaptsn was a mixture of merceptanl obtained frompetroleum. v

To demonstrate the superiority of the organic thionitrites preparedaccording to the procedure of this invention over organic thionitritesobtained according to the process disclosed in the aforesaid Patent No.2,169,188, samples of thinnitrites were obtained by the reaction withnitrosyl chloride of tertiary butyl mercaptan and mixed amyl mercaptansfor comparison with the samples (a) and (b) of Table I above. Inprethese samples the mercahtan was dissolved in a straight rim Dieselfuel oil and gaseous nitrosyl chloride was added slowly withstirring.

' The amount of nitrosyl chloride added was about 20 per cent in excessof the theoretical quantity to convert the mercaptan according to thereaction described in the patent, and the reaction mixture was held at atemperature of about 0 C. during the reaction. The resulting solution ofthe foregoing specification and in the following claims the .term"Diesel fuel oil is intended to-be inclusive of any andall types oi.fuels intended for use in any engine operatingaccordingtotheDieselcycle. r We claim: e 1. "The method of pre aring foruse'in Diesel fuel oil anorganie thionitrite solution which includes:interreacting an organic thiol compound.

an alkali nitrite, and a mineral acid in a nonhomogeneous liquid systemcomprised of an aqueon; phas and a non-aqueous phase, said nonaqueous'phase being a solvent for the thionitrite corresponding to said thiolcompound and posv sensing the additional properties of substantialimmiscibility with water and substantial miscibility with a Diesel fueloil; maintaining the temperature below that at which said thionitriteis.

unstable; and separating the non-aqueous phase containing thethionitrite formed from the'aqueous phase.

solution which includes: interreacting an organic thiol compoimd, analkali nitrite, and a mineral acid in a non-homogeneous liquid system.comprised of an aqueous phase and a'non-aqueous phase, said non-aqueousphase being a solvent for the thionitrite corresponding to the thiolcompound and being substantially immiscible with water; maintaining thetemperature below that at which said thionitrite is unstable; andseparating the aqueous phase from the thionitrite solution.

3. The methodof making an organic thionitrite solution which includes:interreacting an organic thiol compound, an alkali nitrite andhydrochloric acid in a non-homogeneous liquid system comprised of anaqueous phase and a non-aqueous phase, said non-aqueous phase being asolvent for the thionitrite corresponding to the thiol compound andbeing subflantially immiscible thionitrite in the fuel oil afterfiltering to remove with water; the temperature below 2. The method ofmaking an organic thionitrite a non-homogeneous liquid system comprisingan aqueous phase and a non-aqueous solvent for the thionitrite which issubstantially immiscible with water; adding to the reaction mixture amineral acid which will react with the inorganic nitrite to form nitrousacid; agitating the mixture so as to bring about reaction the nitrousacid with the thiol compound, thereby forming the thicnitrite;maintaining the temperature 0! the mixture throughout the, preparationbelow that at which any substantial decomposition of thionitrite willtake place: and separating the nonaqueous phase containing thethlonltrite from the aqueous phase.

5. The method of preparing an organic thionitrite solution whichincludes: adding a mercaptan and an inorganic nitrite to anon-homogeneous liquid system comprising an aqueous phase and anon-aqueous solvent for the thionitritecorresponding to the mercaptan,said non-aqueous solvent being substantially immiscible with water;adding to the reaction mixture a mineral acid which will react with theinorganic nitrit to form nitrous acid; agitating the mixture so as tobring about reaction 01 the nitrous acid with the mercaptan, therebyforming the thionitrite; maintaining the temperature of the mixturethroughout the preparation below that at which any substantialdecomposition of thionitrite will take place; and separating thenon-aqueous solvgnt containing the thionitrite from the aqueous p ate.

8. The method of preparing an organic thic- 5 nitrite solution whichincludes: adding a mercaptide and an inorganic nitrite to anon-homogeneous liquidsystem comprising an aqueous phase and anon-aqueous solvent for the thionitrite corresponding to the mercaptide.said non-aqueous solvent being substantially immiscible with water;adding to the reaction mixture a mineral acid which will react with theinorganic nitrite and the mercaptide to form nitrous acid andm'ercaptan, respectively; a itating the mixture to bring about reaction0! the nitrous acid and morcaptan to form the thionitrite; maintainingthe temperature or the mixture throughout; the preparation below that atwhich any substantial decomposition of thionitrite will take place; andg0 separating the non-aqueous solvent containing the thionitrite fromthe aqueous phase.

7. The method of preparing an organic thienitrite solution whichincludes: inter-reacting an organic thiol compound, an alkali nitrite,and a 'mineral acid in a non-homogeneous liquid system comprising anaqueous phase and a nonaqueous phase consisting of a hydrocarbon fueloil; maintaining the temperatur throughout the preparation below that atwhich the thionitrite is unstable; and separating the hydrocarbon fueloil containing the thionitrite formed by the interreaction of saidreagents from the aqueous phase.

RICHARD s. GEURGE. GEORGE s. CRANDALL. EWIN M. NZGAARD.

